The invention relates to enkephalin analogues or as they are also referred to herein, isosteres.
Enkephalin is the pentapeptide H-Tyr-Gly-Gly-Phe-Met-OH (methionine enkephalin), and since its discovery a great deal of work has been done synthesising analogues with a view to elucidation of the mode of action of enkephalin itself and in particular to clinical use of the analogues.
Much of this work has been specifically in varying the amino acids incorporated, or in analogues where nitrogen atoms replace carbon in the structure of the chain. However we, in seeking compounds with desirable stability in the body and useful biological activity, have used a new approach in which, essentially, we make modifications at the peptide bonds.